1. Field of the Invention
The present invention is directed to a strip of cartridges for use in a powder actuated fastener driving device, and in particular, to a novel flexible strip which carries a plurality of propellant charges which are used to power a fastener driving tool.
2. Description of the Prior Art
Powder or propellant actuated fastener driving tools are used most frequently for driving fasteners into hard surfaces such as concrete. The most common types of this tool are traditionally single fastener, single shot devices; that is, a single fastener is manually inserted into the firing chamber of the tool, along with a single propellant charge. After the fastener is discharged, the tool must be manually reloaded with both a fastener and propellant charge in order to be operated again. Examples of this tool are shown in U.S. Pat. Nos. 4,830,254; 4,598,851; and 4,577,793.
In these types of tools, there are many different types of cartridges used for propellants. For example, U.S. Pat. No. 3,372,643 teaches a low explosive primerless charge consisting of a substantially resilient fibrous nitrocelluose pellet with an igniter portion with a web thickness less than any other dimension of the pellet. U.S. Pat. No. 3,529,548 is directed to a powder cartridge consisting of a cartridge case constructed of two separate pieces which contains a central primer receiving chamber and an annular propellant receiving chamber. U.S. Pat. No. 3,911,825 discloses a caseless propellant charge having an H-shaped cross section composed of a primer igniter charge surrounded by an annular propellant powder charge.
A second type of powder actuated tool has also been used in recent times. This tool still uses fasteners which are individually loaded into the firing chamber of the devices; however, the propellant charges used to provide the energy needed to drive the fasteners are provided on a flexible band of serially arranged cartridges which are fed one-by-one into the combustion chamber of the tool. Examples of these type of tool are taught in U.S. Pat. Nos. 4,687,126; 4,655,380; and 4,804,127.
In the tools heretofore mentioned which use a cartridge strip assembly, there are a variety of strips which are available for use with such tools. U.S. Pat. No. 3,611,870 is directed to a plastic strip in which a series of explosive charges are located in recesses in the strip with a press fit. U.S. Pat. No. 3,625,153 teaches a cartridge strip for use with a powder actuated tool which is windable into a roll about an axis which is substantially parallel to the surface portion of the strip and having the propellant cartridges disposed substantially perpendicular to the surface portion. U.S. Pat. No. 3,625,154 teaches a flexible cartridge strip with recesses for holding propellent charges wherein the thickness of the strip corresponds to the length of the charge contained therein. U.S. Pat. No. 4,056,062 discloses a strip for carrying a careless charge wherein the charge is held in the space by a recess and a tower-shaped wall and is disposed in surface contact with the annular service within the cartridge recess. U.S. Pat. No. 4,819,562 describes a propellant containing device which has a plurality of hollow members closed at one end and a plurality of closure means each having a peripheral rim which fits into the open end of the hollow members of the device.
Recently, several powder actuated tools have been developed which operate in a manner similar to the traditional pneumatic tools; that is, these devices contain a magazine which automatically feeds a plurality of fasteners serially to the drive chamber of the tool, while a strip of propellant charges is supplied serially to the tool to drive the fasteners.
One example of this tool is taught in U.S. Pat. No. 4,821,938. This patent, which teaches an improved version of a tool taught in U.S. Pat. No. 4,655,380, is directed to a powder actuated tool with an improved safety interlock which permits a cartridge to be fired only when a safety rod is forced into the barrel and cylinder assembly and when the barrel and cylinder assembly has been forced rearwardly into its rearward position.
Another example of this type of tool is taught in U.S. Pat. No. 4,858,811. This tool, which is an improved version of the tool taught in U.S. Pat. No. 4,687,126, incorporates a handle, a tubular chamber, a piston, and a combustion chamber within the tubular chamber, the combustion chamber receiving a cartridge in preparation for firing, which upon ignition, propels the piston forwardly for the driving of a nail, a fastener housing located forwardly of the tubular chamber, and provided for shifting a strip of fasteners held by a magazine upwardly through the tool during repeated tool usage.
Consequently, a need exists for a single propellant strip assembly that can be efficiently used in connection with fastener driving tools which have been designed as a replacement for traditional pneumatic tools.
It is thus an object of the present invention to overcome the disadvantages of the above described prior art by the use of a propellant strip assembly in which the propellant charge and sensitizer charge are contained between a flexible carrier strip and a cover strip which is sealed tightly around each individual charge to isolate the charges.
It is also an object of the present invention to provide a propellant strip assembly in which the propellant charge and the sensitizer are physically separated within each chamber to lessen the chance for inadvertant ignition.
It is further an object of the present invention provide a flexible but sturdy propellant strip assembly which can be rolled into a coil for safe and efficient handling.